Messier 40

Discovered on October 24, 1764 by Charles Messier.

Messier: M40.

October 24, 1764. 40. 12h 11m 02s (182d 45' 30") +59d 23' 50"
Two stars very close together & very small, placed at the root of the tail of the Great Bear: One has difficulty to distinguish them with an ordinary telescope of 6 feet [FL]. While searching for the nebula above the back of Ursa Major, reported in the book Figures des Astres, and which is supposed to be for 1660 at 183d 32' 41" right ascension, & 60d 20' 33" northern declination, which Messier couldn't see, he has observed these two stars.

[actually, it seems that Hevelius has observed another nearby binary, 74/75 Ursae Majoris, of mag 5]

[Mem. Acad. for 1771, p. 450 (first Messier catalog)]
The same night on October 24-25, [1764], I searched for the nebula above the tail of the Great Bear [Ursa Major], which is indicated in the book Figure of the Stars, second edition: it should have, in 1660, the right ascension 183d 32' 41", & the northern declination 60d 20' 33". I have found, by means of this position, two stars very near to each other & of equal brightness, about the 9th magnitude, placed at the beginning of the tail of Ursa Major: one has difficulty to distinguish them with an ordinary (nonachromatic) refractor of 6 feet [FL]. Here are their position: right ascension, 182 deg 45' 30", & 59 deg 23' 50" northern declination. There is reason to presume that Hevelius mistook these two stars for a nebula.
[p. 458] 1764.Oct.24. RA: 182.45.30, Dec: 59.23.50.B. Two stars very close to each other, placed at the root of the tail of Ursa Major.

[Hevelius: No. 1496]

Supra tergum nebulosa (above the back [of Ursa Major] there is a nebulosa [nebulous star]).
[actually this is not M40 but 74, 75 Ursae Major]

[Derham: No. 14, from Hevelius]

[Nebulosa, nebulous star] Above the Back of Ursa major
[actually not M40 but 74, 75 Ursae Major]

Bode: Bode 23.

Two closely neighbored nebulous stars. [Taken from Messier]

[Bode 24]
A nebulous star.
[taken from Hevelius; actually not M40 but 74, 75 Ursae Major]

Bode (1782): UMa 74 and UMa 106.

[From: Vorstellung der Gestirne auf XXXIV Kupfertafeln (Introduction to the Stars on 34 Copper Plates), 1782. Here p. 7, plate 6]
UMa 74, after Hevelius. RA: 184:56 [12:19.7], Dec: +59:38. Nebulous [star].
UMa 106, after Messier. Ra: 182:57 [12:11.8], Dec: +59:19. Double star.

William Herschel:

[Unpublished Observations of Messier's Nebulae and Clusters. Scientific Papers, Vol. 2, p. 654]
1799, Aug. 5. Not visible in the finder.
[Dreyer's remark, after quoting Messier's description: Only once looked for by Herschel; Messier only inserted it because he had found it when looking for a nebula alleged to be in that neighborhood.]

Smyth:

[From the description of Delta Ursae Majoris, his No. CCCCXXXVI, 436]
.. This being also the reported site of Hevel's nebula of 1660, and Messier's No. 40, of 1764, I searched for them by fishing, but found only a couple of small stars lying np and sf, with gleams of others. ..

Winnecke: Winnecke 4, WNC 4.

[in Astronomische Nachrichten No. 1738, vol 73, p 147-160, 1869]
No. 4.
Nova. Groombridge 1878. 9 and 9.3 m. 320, Pulk.
Identified as Messier 40 by John Mallas (1966).

Mallas (1966): Identification of M40

[From a letter by John H. Mallas to the Editor of Sky and Telescope, August 1966, p. 83]
Owen Gingerich [stated in] 1960 that this object is a pair of faint stars.
Which pair?
..
[Messier's] position [182 deg 45' 30", +59 deg 23' 50" (1765)], precessed from 1765 to 1950, is 12h 20m.0, +58d 22', which agrees almost exactly with the double star Winnecke 4, magnitudes 9.0 and 9.3, separation 49 seconds of arc. This is an easy pair in my 4-inch refractor at 25x. It was discovered by A. Winnecke in 1863 at Pulkowo Observatory.
Clearly, M40 is identical with Winnecke 4. But the Hevelius object is the 5th-magnitude star 74 Ursae Majoris, more than one degree away, as reference to his star catalogue will show.